U.S. Pat. No. 4,216,741 to Owen R. Moss, discloses an exposure chamber in which a succession of trays serve as distributing means to achieve uniform concentration throughout the chamber of a gas which includes an additive, e.g. aerosol. While intended primarily for the exposure of experimental animals to a controlled atmosphere, it may be used substantially unchanged for other purposes, e.g. the exposure or treatment of plants or the treatment of materials, for example the smoking of meat or fish.
The chamber is characterized by an opening at one end, e.g. the top, and an outlet at the other end, e.g. the bottom. In this configuration the gaseous composition is introduced at the top and deflected towards the side walls of the chamber, trays are arranged horizontally within the chamber, spaced from the side walls and spaced from each other along the mid-plane of the chamber. The gaseous composition flows downwardly through both sets of passages. The trays serve to create a turbulence or circulating movement within the chamber which results in thorough mixing.